Our major goal is to determine the role of genetic factors in the development of prostatic cancer. Our hypothesis is that genetic factors affect secretion of sex-hormones and prolactin and predispose men to the early development of prostatic cancer in response to endogenous hormones and environmental carcinogens. Our probands will be less than 61 years of age when the diagnosis of prostatic cancer is made. We will determine whether (1) the plasma concentrations of sex steroids (estradiol-17Beta, estrone, testosterone and dihydrotestosterone) and prolactin are abnormal in probands and first-order relatives as compared to age-matched in-law controls and the plasma concentrations of the hormone are affected by heredity; (2) the risk of the development of prostatic cancer is higher in first order relatives and maternal and paternal relatives of the index cases than in age-matched controls; (3) the prevalence of some apparent epidemiologic risk variables are observed more commonly in probands and their first order relatives as compared to age-matched controls. The investigation is novel in that the hereditary, endocrine and epidemiologic risk variables for the development of prostatic cancer will be investigated in younger men with the cancer and their relatives. The investigation is feasible because of the availability of a population with large families and a high incidence of prostatic cancer.